Wireless telecommunications networks often use procedures for controlling the signal quality and transmit power levels of forward link signals (i.e., signals transmitted from a base station to a mobile station) and/or reverse link signals (i.e., signals transmitted from a mobile station to a base station).
For example, in a code division multiple access (CDMA) network, the wireless service provider typically sets a target frame error rate (FER) in order to specify a desired signal quality of forward link and/or reverse link signals. Thus, the target FER may be used as a quality control parameter to control the signal quality of forward link and/or reverse link signals. Typically, the same target FER is used for all mobile stations being served by the wireless service provider in a given area. If the actual FER rate in a received forward link or reverse link signal is above the target FER, then the transmit power level of the signal may be increased. If the actual FER in the received signal is below the target FER, then the transmit power level of the signal may be decreased. In this way, the transmit power level of a forward link or reverse link signal may be increased or decreased (typically within minimum and maximum transmit power levels set by the wireless service provider) so as to achieve the signal quality represented by the target FER.
The control of transmit power levels to achieve a target FER may occur through an “inner loop” process and an “outer loop” process. In a conventional “inner loop” process, a receiving device receives a wireless signal transmitted by a transmitting device. The receiving device periodically assesses the strength of the received signal, such as by determining the signal-to-noise ratio (SNR), and compares the observed value to a setpoint. If the observed value is lower than the setpoint, the receiving device instructs the transmitting device to increase the transmit power of the wireless signal. If the observed value is higher than the setpoint, the receiving device instructs the transmitting device to lower the transmit power of the wireless signal.
In a conventional “outer loop” process, the receiving device periodically measures an observed FER in the received signal and compares the observed FER to a target FER. The receiving device may adjust the setpoint used for power control based on the comparison between the observed FER and the target FER. If the observed FER is higher than the target FER, the receiving device may increase the setpoint, which may lead to a corresponding increase in the transmit power level via the “inner loop” process. If the observed FER is lower than the target FER, the receiving device may decrease the setpoint, which may lead to a corresponding decrease in the transmit power level via the “inner loop” process.